The present invention relates to the use of novel compounds which make it possible in particular to obtain films on a substrate, and to their application in particular in cosmetics or in pharmaceuticals.
Hyperbranched polymers and dendrimers are well known in the prior art. Hyperbranched polymers are molecular constructions having a branched structure, generally around a core. Their structure generally lacks symmetry, the base units or monomers used to construct the hyperbranched polymer can be of diverse nature and their distribution is non-uniform. The branches of the polymer can be of different natures and lengths. The number of base units, or monomers, may be different depending on the different branching. While at the same time being asymmetrical, hyperbranched polymers can have: an extremely branched structure, around a core; successive generations or layers of branching; a layer of end chains.
Hyperbranched polymers are generally derived from the polycondensation of one or more monomers ABx, A and B being reactive groups capable of reacting together, x being an integer greater than or equal to 2, but other preparation processes may be envisaged. Hyperbranched polymers are characterized by their degree of polymerization DP=1-b, b being the percentage of non-terminal functionalities in B which have not reacted with a group A. Since the condensation is not systematic, in contrast with the synthesis of dendrimers, the degree of polymerization is less than 100%. An end group T can be reacted with the hyper-branched polymer to obtain a particular functionality on the ends of chains.
Several hyperbranched polymers can be combined together, via a covalent bond or another type of bonding, by means of their end groups. Such polymers, known as bridged polymers, fall within the definition of the hyperbranched polymers according to the present invention.
Dendrimers are highly branched polymers and oligomers having a well-defined chemical structure. As a general rule, dendrimers comprise a core, a given number of generations of branches, or spindles, and end groups. The generations of spindles consist of structural units which are identical for the same generation of spindles and which may be identical or different for different generations of spindles. The generations of spindles extend radially in a geometrical progression from the core. The end groups of a dendrimer from the Nth generation are the end functional groups of the spindles of the Nth generation or end generation.
The definition of dendrimers given above includes molecules containing symmetrical branching; it also includes molecules containing non-symmetrical branching, such as, for example, dendrimers whose spindles are lysine groups, in which the branching of one generation of spindles on the preceding generation takes place on the xcex1 and xcex5 amines of lysine, which leads to a difference in the lengths of the spindles of different branching.
Dense star polymers, starburst polymers and rod-shaped dendrimers are included in the present definition of dendrimers. The molecules known as arborols and cascade molecules also fall within the definition of dendrimers according to the present invention.
Several dendrimers can be combined together, via a covalent bond or another type of bonding, by means of their end groups to give species known as bridged dendrimers or dendrimer aggregates. Such species are included in the definition of dendrimers according to the present invention.
Dendrimers can be in the form of an assembly of molecules of the same generation, which are referred to as monodisperse assemblies; they can also be in the form of assemblies of different generations, known as polydisperse assemblies. The definition of dendrimers according to the present invention includes both monodisperse and polydisperse assemblies of dendrimers.
French patent application FR 97/04085 in the name of the Applicant in particular discloses novel polymers chosen from hyperbranched polymers and dendrimers, comprising functional groups corresponding to the following formula: 
in which
Y represents an oxygen atom or an NH group,
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkanediyl group, this group optionally being interrupted with one or more hetero atoms and/or substituted with a function chosen from amino, acylamino, carboxylic acid and ester.
These polymers find an application in particular in cosmetics and dermatology as antioxidants or reducing agents.
Now, the Applicant has found, surprisingly, that the said polymers can also be used to allow the preparation of compositions, in particular cosmetic or pharmaceutical compositions, which make it possible to obtain a film when they are deposited on a substrate.
Thus, a subject of the present invention is the use of at least one compound chosen from hyperbranched polymers and dendrimers, comprising at least one group of formula: 
in which:
Y represents an oxygen atom or an NH group, and
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkanediyl group, this group optionally being interrupted with one or more hetero atoms and/or substituted with a function chosen from:
amino (xe2x80x94NH2),
acylamino (xe2x80x94NHxe2x80x94COxe2x80x94R) in which R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group,
carboxylic acid (xe2x80x94COOH),
ester (xe2x80x94COOR) in which R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group, as film-forming agent.
Another subject of the invention is a film-forming composition comprising at least one compound chosen from hyperbranched polymers and dendrimers, comprising at least one group of formula (I), the said composition being able to be obtained by oxidation of a composition comprising at least one polymer chosen from hyperbranched polymers and dendrimers comprising at least one group of formula (II).
Another subject of the invention is the use of at least one polymer chosen from hyperbranched polymers and dendrimers comprising at least one group of formula (II), for the preparation of a film-forming composition comprising at least one compound chosen from hyperbranched polymers and dendrimers comprising at least one group of formula (I), or of a composition as defined above.
Another subject of the invention is a process for obtaining a film on a support, in which a composition as defined above is applied to the said support.
Another subject of the invention is a process for obtaining a film on a support, in which a composition comprising a polymer is applied to the said support, this polymer being chosen from hyperbranched polymers and dendrimers comprising at least one group of formula (II), and the said composition is oxidized during or after its application to the said support.
The prior art discloses a certain number of film-forming agents for obtaining films. In particular, mention may be made of film-forming polymers which may be radical-mediated polymers or polycondensates, among which mention may be made of acrylic polymers and polyurethanes. Such polymers are used in particular in the field of hair care, for example in lacquers, or in the field of make-up, for example in mascaras or nail varnishes in an organic solvent medium.
However, these film-forming agents have certain drawbacks. In particular, these film-forming agents form films as soon as they are deposited on the support.
In contrast, the compounds according to the invention form films only in oxidizing medium. Thus, it is possible to apply an aqueous or aqueous-alcoholic solution, for example, of thiols (II) as a thin layer on a support, and then, at the time chosen, to chemically oxidize or to allow to oxidize freely, in particular in open air, the said thiols into compounds (I), which compounds will form, on drying, on the support, a highly adherent and water-washable film.
The compounds according to the invention allow the production of films similar to those obtained with film-forming polymers of the prior art.
Depending on the oxidation conditions, the quality of the films obtained can vary: tacky or non-tacky films, glossy or matt films, etc.
Thus, as a function of the oxidation conditions, glossy films can readily be obtained, which adhere well to the support and are non-tacky; when such films comprise a pigment or a dye, they do not mark the support on which they are deposited since they do not bleed.
The compounds which can be used within the scope of the invention are chosen from hyperbranched polymers and dendrimers, and comprise at least one group of formula (I): 
in which:
Y represents O or NH,
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkanediyl group, this group optionally being interrupted with one or more hetero atoms and/or substituted with a function chosen from:
amino (xe2x80x94NH2) optionally in the form of a salt of an inorganic or organic acid,
acylamino (xe2x80x94NHxe2x80x94COR) in which R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group,
carboxylic acid (xe2x80x94COOH),
ester (xe2x80x94COOR) in which R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group.
Preferably, the compound according to the invention is chosen from hyperbranched polymers, and in particular polyethyleneimine, comprising at least one group of formula (I).
Preferably, Y represents an oxygen atom.
Preferably, the hetero atoms are chosen from oxygen and nitrogen (O and N).
Preferably, A is a methylene, ethylene, propylene, methylpropylene, ethylpropylene, tetramethylene, pentamethylene, hexamethylene, phenylene or phenyldiyl group.
Advantageously, A represents a radical corresponding to one of the formulae (a) to (d) below:
(a) xe2x80x94CHR1xe2x80x94CHR2xe2x80x94CHR3xe2x80x94
(b) xe2x80x94CHRxe2x80x21xe2x80x94CHRxe2x80x22xe2x80x94CHRxe2x80x23xe2x80x94CHRxe2x80x24xe2x80x94
(d) xe2x80x94(CHRxe2x80x2xe2x80x31)kxe2x80x94(CHRxe2x80x2xe2x80x32)xe2x80x94CH(CO2H)xe2x80x94NHxe2x80x94
xe2x80x83in which
R1, R2, R3, Rxe2x80x21, Rxe2x80x22, Rxe2x80x23 and Rxe2x80x24, Rxe2x80x2xe2x80x31 and Rxe2x80x2xe2x80x32, which may be identical or different, represent: a hydrogen atom; a linear, branched or cyclic, saturated or unsaturated C1-C6 alkyl radical; an amino (xe2x80x94NH2) radical; a carboxylic acid (xe2x80x94COOH) radical; a C1-C10 alkylamino radical; a C1-C10 acylamino radical;
Rxe2x80x31, Rxe2x80x32, Rxe2x80x33 and Rxe2x80x34, which may be identical or different, represent: a hydrogen atom; a linear or branched, saturated or unsaturated C1-C4 alkyl radical, the arrows indicating the positions of the substitutions;
k is an integer, preferably 0 or 1.
Preferably, A is chosen from the following groups:
xe2x80x94CH2xe2x80x94CH(CO2H)xe2x80x94NHxe2x80x94; xe2x80x94(CH2)2xe2x80x94(CH3CONH)CHxe2x80x94; xe2x80x94(CH2)3xe2x80x94 and
xe2x80x94CH2xe2x80x94CH(NHxe2x80x94COxe2x80x94CH3)xe2x80x94.
The compounds defined above can be obtained in particular by oxidation of the polymers described in patent application FR 97/04085, the content of which is incorporated by way of reference, and which are chosen from hyperbranched polymers and dendrimers, comprising functional groups corresponding to formula (II): 
in which:
Y represents O or NH,
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkanediyl group, this group optionally being interrupted with one or more hetero atoms and/or substituted with a function chosen from amino, acylamino, carboxylic acid and ester.
The oxidation can be carried out by any known means, for example in air or using a common oxidizing agent such as hydrogen peroxide.
The oxidation step allows the formation of intramolecular and intermolecular disulphide bridges, starting with thiol functions, according to the scheme below: 
The formation of disulphide bridges brings about a xe2x80x9cpseudo-crosslinkingxe2x80x9d of the starting compounds A, which is reflected in the formation of compounds B which make it possible to obtain films when they are deposited on a substrate.
The oxidation step is preferably carried out in the presence of water, for example in aqueous or aqueous-alcoholic medium.
After application on a substrate, it is thus possible to obtain films containing only one or more compounds B according to the invention and optionally starting compounds A that have not reacted, when the oxidation is only partially performed.
It has also been found that it is possible to incorporate, before oxidation, water-soluble or water-insoluble additives into the aqueous or aqueous-alcoholic medium while at the same time retaining the possibility of obtaining an adequate film.
Among the additives which can be incorporated, mention may be made of water-soluble dyes such as Rhodamine; water-soluble cosmetic or pharmaceutical active agents; water-insoluble products which have in particular optical properties such as phosphorescence or fluorescence; pigments; fillers; sunscreens; water-insoluble cosmetic or pharmaceutical active agents.
It has moreover been found that the solid additives, pigment particles or fillers, for example, were fully dispersed homogeneously in the film; they are fully enclosed in the structure of the film. There is no releaase of the particles, and the films are not tacky.
It is known that the properties of the films obtained depend on the oxidation conditions, in particular the concentration of starting thiol-containing polymer, the number of thiol functions in the said thiol-containing polymer, the molar mass of the said polymer and/or the pH of the aqueous/aqueous-alcoholic medium before oxidation.
Thus, the films can be prepared directly using an aqueous solution or an aqueous-alcoholic solution of thiol-containing polymer. During drying, the thiol functions will be oxidized to disulphides. It has been observed that, in this case, the films obtained may be visually non-uniform and may remain tacky.
When an aqueous or aqueous-alcoholic solution of thiol-containing polymer is oxidized chemically and when a film is prepared using this liquid oxidized solution, the film obtained after drying is generally very uniform, with a very uniform surface, glossy, transparent, colourless, highly adherent and may be brittle when it is desired to detach it. These films are not water-resistant.
It is thus possible to obtain a composition which can form films and which can be used in its native form, as a cosmetic or pharmaceutical composition, or incorporated into a composition, in particular a cosmetic or pharmaceutical composition, which can then comprise a cosmetically or pharmaceutically acceptable medium.
The said cosmetic or pharmaceutical composition can be in any form which is suitable for topical application, in particular in the form of aqueous or aqueous-alcoholic gels; in the form of water-in-oil, oil-in-water or multiple emulsions, of more or less thickened liquid consistency, such as a milk or cream; sprays or aerosol mousses; sticks or tubes; solutions or liquid dispersions.
A person skilled in the art knows how to prepare these compositions according to the usual methods, on the basis of his or her general knowledge.
In particular, these compositions can contain adjuvants usually used in the cosmetics or pharmaceuticals fields, such as oils, waxes or other common fatty substances; surfactants; moisturizers; emollients; sunscreens; hydrophilic or lipophilic active agents such as ceramides; free-radical scavengers; polymers; proteins; bactericides; sequestering agents; antidandruff agents; antioxidants; preserving agents; basifying or acidifying agents; fragrances; fillers; dyestuffs; cosmetic or pharmaceutical active agents. The amounts of these various adjuvants are those conventionally used in the fields under consideration and can readily be determined by a person skilled in the art.
Needless to say, a person skilled in the art will take care to select this or these optional additional adjuvant(s), and/or the amount thereof, such that the advantageous properties of the composition according to the invention are not, or are not substantially, adversely affected by the envisaged addition.
The compositions according to the invention are film-forming and can thus be used to form a film on a support, chosen in particular from the skin, mucous membranes, semi-mucous membranes, the nails and the hair of human beings.
The compositions according to the invention are, for example, lotions, milks or creams for skincare or haircare; make-up-removing creams, lotions or milks; foundation bases; antisun or after-sun lotions, milks or creams; artificial tanning lotions, milks or creams; shaving creams or foams; aftershave lotions; body hygiene compositions such as deodorant sticks or creams; shampoos; hair products for maintaining the hairstyle or for shaping the hair such as styling gels; hair-colouring products; lipsticks; mascaras or eyeliners which may be for treatment purposes; nail varnishes or nailcare products.